1. Field of the Invention
The present invention relates to a multi-cylinder reciprocating compressor, and more particularly, to a multi-cylinder reciprocating compressor suitable for use in a refrigeration circuit of an automotive air conditioning system.
2. Description of the Related Art
This type of multi-cylinder reciprocating compressor is disclosed, for example, in Japanese Utility Model Publication No. H06-25576. The compressor disclosed in this publication has a plurality of compression chambers, a discharge chamber, and discharge valves associated with the respective compression chambers to allow refrigerant compressed in the respective compression chambers to be discharged into the discharge chamber.
More specifically, each discharge valve has a valve reed attached to a valve plate located between the compression chambers and the discharge chamber. The valve reed opens and closes a discharge hole formed through the valve plate. The discharge valve further includes a retainer for regulating the opening of the valve reed, and the retainer has a stopper surface facing the valve plate.
When the pressure of the refrigerant in the compression chamber surpasses the valve closing force of the valve reed, the refrigerant causes the free end of the valve reed to lift from the valve plate toward the retainer. As a result, the discharge hole opens, allowing the refrigerant in the compression chamber to be discharged into the discharge chamber through the discharge hole. When the refrigerant is discharged in this manner, the valve reed abuts against the stopper surface of the retainer. Thus, the stopper surface serves to regulate the lift of the free end of the valve reed, that is, the opening of the valve reed.
The stopper surface of the retainer is inclined with respect to the valve plate, as viewed in cross section of the valve reed. Accordingly, when the valve reed is lifted, the valve reed comes into close contact with the stopper surface while being twisted about a longitudinal axis thereof, so that the lift of the valve reed, that is, the distance between the free end of the valve reed and the valve plate, varies along the width direction of the valve reed. Specifically, the lift of the valve reed increases from one side edge thereof toward the other. Thus, the refrigerant discharged from the discharge hole flows mainly toward the other side edge of the valve reed, whereby directivity is imparted to the discharge of the refrigerant.
In the aforementioned discharge valve, therefore, stable opening/closing operation of the valve reed can presumably be ensured by directing the discharge direction of the refrigerant such that the refrigerant discharged from the discharge hole exerts no adverse influence on the opening/closing of the valve reeds of the adjacent discharge valves.
Since the valve reed has relatively high rigidity against twisting, however, the valve reed is insufficiently twisted when lifted, and it is difficult to bring the valve reed into satisfactorily close contact with the stopper surface of the retainer.
Consequently, the valve reed repeatedly strikes on the stopper surface when lifted, causing vibrations. Such vibrations not only produce unpleasant noise but impede smooth discharging of the refrigerant from the compression chamber, which lowers the compression efficiency of the compressor.